Apparatus for lowering machine into table



Sept; 1969 HIROSHI TOMURO 3,465,695

APPARATUS FOR LOWERING MACHINE INTO TABLE Filed Aug. 29, 1967 2 Sheets-Sheet 1 INVENTOR HIRDSHI TD -PO ATTORNEYS Sept. 9, 1969 HIROSHI TOMURO 3,465,695.

APPARATUS FOR LOWERING MACHINE INTO TABLE Filed Aug. 29, 1967 2 Sheets-Sheet 2 FIG. 8

INVENTOR NIROSHI TDHLLRO ATTORNEYS United States Patent C) 3,465,695 APPARATUS FOR LOWERING MACHINE INTO TABLE Hiroshi Tomuro, 695 2-chome, Tamagawa Den-en-Chofu, Setagaya-ku, Tokyo, Japan Filed Aug. 29, 1967, Ser. No. 664,146 Claims priority, application Japan, Sept. 5, 1966, 41/58,163 Int. Cl. B25h 1/00; D05b 75/06; A47b 29/00 US. Cl. 108161 6 Claims ABSTRACT OF THE DISCLOSURE Apparatus for lowering a machine, suchgas a sewing machine, a typewriter or the like, into a machine table, which employs a balancing spiral spring which decreases its tension as it is drawn out, in order to substantially balance the actual weight of the machine which gradually decreases as the machine is lowered into the machine table.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to an apparatus for lowering a machine, such as a sewing machine, a typewriter or the like, into a machine table when the machine is not used.

Description of the prior art In general, it requires a substantial manual force for a user to lift a machine from its lowered position in the table to the operative position on the table. In order to relieve the force required to lift the machine, a helical spring or springs have been used to balance the weight of the machine. However, a helical spring increases its tension as it is stretched, so that the tension of the helical spring is greatest when the machine is lowered and it gradually decreases as the machine is lifted to the opera tive position. Accordingly, such helical spring cannot constantly balance the actual weight of the machine which gradually increases as the machine is lifted to its operative position. Furthermore, such helical springs should be sufficiently so weak that the tension of the spring is surpassed by the actual weight of the machine when it is lowered into the table, otherwise the machine may tend to rise out of the table. In order to avoid such defects of the helical spring heretofore used to balance the weight of the machine, it has been proposed to employ a toggle linkage to multiply the lifting force of the spring so as to compensate for the decrease of the tension of the spring as the machine is raised from the lowered position to the operative position. However, such toggle linkage is very complicated and expensive.

SUMMARY OF THE INVENTION The present invention aims at overcoming the abovementioned difiiculties of the conventional apparatus for lowering a machine into a table.

It is an object of the invention to provide an apparatus for lowering a machine into a machine table in which the actual weight of the machine is substantially balanced by a balancing spring so that the machine can be lowered and raised very easily.

It is another object of the invention to provide an apparatus of the above kind which is very simple in construction and can be manufactured with very low cost.

In accordance with an aspect of the present invention, an apparatus for lowering a machine into a table comprises a balancing spiral spring which decreases its tension as it is drawn out, in order to constantly balance the actual weight of the machine.

Patented Sept. 9, 1969 BRIEF DESCRIPTION OF THE DRAWINGS The drawings illustrate an embodiment of the present invention, in which:

FIG. 1 is a side view of a sewing machine embodying the apparatus according to the present invention;

FIG. 2 is an end view seen from the right side of FIG. 1;

FIGS. 3-7 show the parts of the apparatus according to the invention;

FIG. 3 is a perspective view of an attaching member;

FIG. 4 is a perspective view of a supporting shaft having spiral springs mounted on both ends thereof;

FIG. 5 is a side view of a spring blank;

FIG. 6 is a perspective view of a balancing spiral spring constructed from the spring blank as shown in FIG. 5;

FIG. 7 is a developed view of a modified form of a balancing spiral spring;

FIG. 8 is a side view of the stopping mechanism; and

FIG. 9 is a front View of the stopping mechanism shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention will be explained with reference to the preferred embodiment shown in the drawings. Referring to FIGS. 1 and 2 which illustrate a sewing machine embodying the apparatus according to the present invention, 1 designates a head of the sewing machine and 2 designates a table. The head 1 is pivotally supported at 3 on the table 2 and is swingable between the lowered position or housed position in the table and the raised position or operative position on the table. At the operative position the machine head is placed on a supporting plate 5, which is pivotally mounted at 4 on the table 2.

When it is desired to lower the machine head into the table, the head 1 is slightly raised and the supporting plate 5 is swung upwardly as shown in FIG. 2, whereby the head becomes free to move downward into the table. The head 1 has a substantial weight, so that a substantial manual force is required for a user to lower or raise the head into or out of the table. Assuming that the weight of the head is 13 kg., the actual weight at the leg 6 of the head is about 5 kg. in the completely lowered position and about 7.5 kg. in the operative position. In order to balance the actual weight of the machine, it is required to use a balancing spring having a strength corresponding to such varying loads of the machine head.

The present invention employs a special spiral spring which gradually decreases its tension as it is drawn out, in order to constantly balance or slightly overbalance the varying actual weight of the machine. FIGS. 3-7 show the parts of the apparatus according to the present invention. FIG. 3 shows an attaching member 14 which is mounted on a machine table and on which an end of a spiral spring is attached. FIG. 4 shows a supporting shaft 8 which is adapted to engage with the legs 6 of the head 1 and has spiral springs 9 on both ends thereof.

The spiral spring 9 is so constructed that it gradually decreases its tension as it is drawn out. According to one example of the present invention, such spiral spring can be manufactured by first preparing a required length of strip of spring material, forming a spiral spring from this strip in the usual manner with the radius of curvature of the spiral gradually increasing from the inside to the outside as shown in FIG. 5, then rewinding said spiral so that the larger radius of curvature is inside and the smaller radius of curvature is outside as shown in FIG. 6, securing an end plate 10 on the free end of said rewound spiral and mounting the rewound spiral on a flanged sleeve 11. The inside portion having larger radius of curvature of said rewound spiral should have an inside diameter which is equal to or slightly smaller than the outside diameter of said sleeve 11. The spiral spring 9 mounted on the sleeve 11 is rotatably fitted on each end of said supporting shaft 8, stop rings 12 being provided to prevent the axial movement of the sleeves on the supporting shaft. Due to such construction of the spiral spring 9, the tension of the spring is larger at the outside portion having the smaller radius of curvature and smaller at the inside portion having the larger radius of curvature, that is, the tension of the spring gradually decreases as it is drawn out. Accordingly, this spring can be utilized to constantly balance the actual weight of the machine which gradually decreases as it is lowered into the cabinet.

FIG. 7 shows another example'of the spiral spring, which is manufactured by preparing a tapered belt of spring material as shown in FIG. 7, winding this tapered belt at a constant radius of curvature in the form of a spiral spring with its narrow end inside, securing an end plate on the free end (wide end) of the belt and mounting the spiral spring on a flanged sleeve. This spiral spring can be fitted on each end of the supporting shaft 8 as shown in FIG. 4 and serves the same purpose as the spiral spring shown in FIGS. and 6.

The balancing means comprising the spiral springs 9 mounted on the supporting shaft 8 is supported at both ends on the underside of the machine table 2 by means of attaching members 14 as shown in FIG. 3 which are mounted on the mounting plates 13, respectively, which are fixed on the underside of the table 2, as shown in FIG. 1. The attaching member 14 has a semicircular groove 15 in the inside wall for receiving the supporting shaft 8 and a hook 16 for fixing the end plate of the spiral spring 9. The supporting shaft 8 is pulled upward by the action of the spiral spring 9 and is held against the semicircular grooves of the attaching members 14. Preferably, the spiral springs 9 are held under slightly drawn-out state from the sleeve 11, that is, they have initial tension, when the supporting shaft 8 bears against the semicircular grooves 15. The leg 5 of the machine head 1 has a semicircular groove 17 which is adapted to engage with the shaft 8. The weight of machine head 1 is supported at the legs 6 on the supporting shaft 8, which is supported by the springs 9. At the operating position of the sewing machine, the machine is supported on the plate 5, as explained above.

Thus, the weight of the machine is balanced by the spiral springs 9 so that the actual weight becomes substantially zero when lowering or raising the machine. Also, the spiral spring is prevented from the transverse movement by the flanges formed on the sleeve 11, so that the supporting shaft 8 is always maintained at the proper transverse position without necessitating any guiding means.

Although the apparatus according to the present invention is so constructed that the actual weight of the machine becomes substantially zero by using the spiral springs which have tension corresponding to the actual weight of the machine as described above, it can be also so constructed that the tension of the springs 9 is slightly higher than the actual weight of the machine, say 0.2 or 0.3 kg., so that the machine is automatically raised from the housed position to the operating position. In such a construction, the machine can be lowered with a small manual force, such as 0.2 or 0.3 kg. into the machine table. In order to hold the machine in the table, a stopping mechanism as shown in FIGS. 8 and 9 is used.

The stopping mechanism as shown in FIGS. 8 and 9 comprises a wire spring 20 fixed at the upper end of a movable plate 19 which is pivotally supported on the rear wall of the machine table. Said wire spring has a semicircular portion 21 which is adapted to engage with the supporting shaft 8 to hold said shaft in the lowered position. A flexible wire 22, which is attached to the lower end of the movable plate 19, extends around a guide roller 23 to the front side of the machine, where it is fixed to an operating knob 24. The movable plate 19 is normally biased to the vertical position by a tension spring 25 (see, FIG. 9).

When the machine head is depressed by the manual force, the supporting shaft 8 comes into contact with the end of the wire spring 20 as shown by dotted line in FIG. 8 to resiliently deflect the wire spring 20 downward and then engages with the semicircular portion 21. Thus the supporting shaft is held in the lowered position by the wire spring 20. In order to raise the machine head to the operative position, it is only necessary to pull the knob 24 to rotate the movable plate 19 about the pivot 18 so as to disengage the semicircular portion 21 of the wire 20 from the supporting shaft 8. The machine head is gradually raised by the action of the spiral springs 9 which slightly overbalances the actual weight of the machine head. Preferably the knob 24 has stepped portions which can selectively engage with the front side of the machine table so as to adjust the slight variation of the length of the flexible wire 22 so that the movable plate 19 is normally held in the vertical position.

It will be understood from the above explanation that in accordance with the present invention the actual weight of the machine is balanced or slightly overbalanced by the spiral springs which decrease their tension as they are drawn out from their mounting sleeves, so that the machine can be lowered or raised into or out of the table with very small manual force or the machine can be automatically raised to the operative position. Thus the present inventionv provides a great convenience in the operation of the machine.

It will be understood that although the invention has been described in detail with reference to a sewing machine, it can be also applicable to a typewriter or the like which can be lowered into a machine table.

I claim:

1. In a machine of the type comprising a table having a top and a machine head having a base hingedly connected at one side with the top of said table and having its opposite side free to be raised and lowered from a down position in said table to a raised or operative position on the top of said table; an apparatus for balancing the weight of said machine head comprising a gradually decreasing force spring connected between the table top and said opposite side of the base of the machine head to apply a gradually decreasing force tending to raise said machine head toward the table top, said gradually decreasing force of said spring being so selected as to substantially balance the actual load of the machine head which gradually decreases as it is lowered from the raised position to the down position. 1

2. In a machine of the type comprising a table having a top and a machine head having a base hingedly connected at one side with the top of said table and having its opposite side free to be raised and lowered from a down position in said table to a raised or operative position on the top of said table; an apparatu for balancing the weight of said machine head comprising a gradually decreasing force spring connected between the table top and said opposite side of the base of the machine head to apply a gradually decreasing force tending to raise said machine head toward the table top, said gradually decreasing force of said spring being so selected as to slightly overbalance the actual load of the machine head which gradually decreases as it is lowered from the raised position to the down position, and a stopping mechanism for holding the machine head at the down position.

3.- An apparatus for balancing the weight of a machine head according to claim 1, in which said gradually decreasing force spring consists of a strip of spring material spirally wound on a drum mounted on the table top and having its free end attached to said opposite side of the base of the machine head, said Strip being firstly formed with the radius of curvature gradually increasing from the inside to the outside and then rewound so that the larger radius of curvature is inside and the smaller radius of curvature is outside.

4. An apparatus for balancing the weight of a machine head according to claim 2, in which said gradually decreasing force spring consists of a strip of spring material spirally wound on a drum mounted on the table top and having its free end attached to said opposite side of the base of the machine head, said strip being firstly formed with the radius of curvature gradually increasing from the inside to the outside and then rewound so that the larger radius of curvature is inside and the smaller radius of curvature is outside.

5. An apparatus for balancing the weight of a machine head according to claim 1, in which said gradually decreasing force spring consists of a strip of spring material spirally wound on a drum mounted on the table top and having its free end attached to said opposite side of the base of the machine head, said strip being formed as a tapered belt which is wound in a spiral spring form at a constant radius of curvature with its narrow end inside. 6. An apparatus for balancing the weight of a machine head according to claim 2, in which said gradually decreasing force spring consists of a strip of spring material spirally wound on a drum mounted on the table top and having its free end attached to said opposite side of the base of the machine head, said strip being formed as a tapered belt which is wound in a spiral spring form at a constant radius of curvature with its narrow end inside.

References Cited UNITED STATES PATENTS 2,700,585 1/1955 Strocco 112217.1 2,711,940 6/ 1955 Hochman 31230 2,789,875 4/1957 Van Ordt 312-30 2,790,690 4/ 1957 James 31230 3,188,986 6/1965 LaVigne 108136 JAMES T. MCCALL, Primary Examiner U.S. Cl. X.R. 3 l2-30 

